[Wien] 4f and LDA+U

[laurent.baudery]

Dear Stefan,

Thank you for the explanations.

I actually meant de-localized states instead of localized. I had already tried an Ueff of 8.5 ev, the result is that the split of the f  states was more important and in the same manner as you had described.


Regarding the two different values of  Ef, I checked  case.inorb and it seems ok. U is applied only on the  f states of Nd:

  1  2  0                     nmod, natorb, ipr
PRATT  1.0                    BROYD/PRATT, mixing
  1 1 3                          iatom nlorb, lorb
  2 1 3                          iatom nlorb, lorb
   1                              nsic 0..AFM, 1..SIC, 2..HFM
   0.625 0.00        U J (Ry)   Note: we recommend to use U_eff = U-J and J=0
   0.625 0.00        U J (Ry)   Note: we recommend to use U_eff = U-J and J=0
 
the calculation are performed as follow :

runsp_lapw -p -fc 0.1
save_lapw case1
runsp_lapw -orbc -p -fc 0.1
save_lapw case2
runsp_lapw -orb -p -fc 0.1.

x lapw2 -qtl -c -up  -p
x lapw2 -qtl -c -dn  -p

Is it correct ?


Thank you for your help,
Laurent Baudery

>> I performed spin-polarized calculations on NdTiO3 compound and as excepted the fermi level  lies at the 4f states (due to the strong localisation).

>(Probably a word is missing in your last sentence, which gives it the opposite meaning? ==> de-localization) The reason why LDA puts the 4f states at the fermi level is that it cannot sufficiently localize these states. They are hence (incorrectly) described as itinerant states.

>> Thereafter, I performed spin-polarized LDA+U (Ueff=6.5 ev) calculations

>This value of U might be somewhat at the lower side for lanthanides. Try 8.5 eV (see http://link.aps.org/doi/10.1103/PhysRevB.74.014409 and http://link.aps.org/doi/10.1103/PhysRevB.77.155101 , and references therein).

>> which split the 4f (up) states : the occupied states down by 3 ev below the Ef and empty states rises by about 5 ev above the Ef. I got two different values of Ef(up) and Ef(dn).
> >
> >By applying Ueff=6.5 ev I expected a little split that will let the 4f occupied states at the top of the valence band (around the Ef).    Can someone give me a comment about this ? Are also normal to have two different values of Ef (up and dn)?

>Such two different values of Ef I've never seen. Are you sure you aren't by mistake making an applied field calculation (which is another input number in the same case.inorb file you use for LDA+U).

>What should happen for Nd is that all dn-states (which are unoccupied) move up and find themselves all above Ef, while the up-states split in an occupied part several eV below Ef and an unoccupied part several eV above Ef.

Stefaan

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